The total land area of Castillejos covers an area of 17,744 hectares. Out of this, an approximate area of 3,894.44 hectares or 21.95% is devoted to agriculture. The agricultural land area is utilized for planting temporary crops (rice, corn, vegetables, root crops, banana & dragon fruit), permanent crops (fruit trees), inland resources (fishery), livestock and poultry area (commercial), build-up area and others. An area of 1,729.72 hectares is mainly devoted for rice production of which 1,056.40 hectares are irrigated. The rest are rainfed and uplands. These non-irrigated ricelands are those that cannot easily take advantage of the irrigation program of the government. Root crops such as sweet potato and cassava are the major agricultural product of the municipality which occupies a land area of 607 hectares and 14.75 hectares respectively. Fast growing agricultural area in the municipality which occupy mostly gently sloping land are the fruit trees plantation or orchard.

The fish requirement of Castillejos is source out from its fresh water through the Pamatawan River and fishponds which are approximately 7.72 hectares. Most of those fishponds are located in Barangay Looc and San Agustin. The main fresh water species are tilapia, mudfish, catfish and others

One promising activity in the place is livestock and poultry raising. At present, there are three (3) poultry producers in the municipality while on hog raising, there are five (5) piggery farms. Others are small growers and backyard raisers who also contribute to the production and supply of the livestock and poultry raising activities.

Castillejos has a forest area of 12,817.19 hectares of which are forestland, timberland and public forest. Hardwood forest species such as narra, maligpaho, calantas, apitong, tanguile and guijo are abundant in the mountaneous portion of Castillejos, specifically in Sitio Canaynayan, Barangays San Pablo, Looc and San Agustin. These forested areas also yield minor products such as bamboo, rattan, jungle vines and cogon.